Yes, thanks, I figured this myself (hooray!) and I'm up to the next error at this moment.

>Look at this in your code,
>
>You repeated colPrice in [//Order Item Total Price] part instead of colTotalPrice data grid view column.
>It seems you did a COPY - PATE
>
> //Order Item Price
> DataGridCustomTextBoxColumn colPrice = new DataGridCustomTextBoxColumn();
> colPrice.Owner = this.grdOrderItems;
> colPrice.HeaderText = "Price";
> colPrice.MappingName = "Price";
> colPrice.Width = ((this.grdOrderItems.Width * 24) / 100);
> colPrice.Alignment = HorizontalAlignment.Right;
> // Setup table mapping name
>
> //Order Item Total Price
> DataGridCustomTextBoxColumn colTotalPrice = new DataGridCustomTextBoxColumn();
> colPrice.Owner = this.grdOrderItems;
> colPrice.HeaderText = "Total";
> colPrice.MappingName = "TotalPrice";
> colPrice.Width = ((this.grdOrderItems.Width * 24) / 100);
> colPrice.Alignment = HorizontalAlignment.Right;